#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"
#include "LiquidCrystal.h"
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);

float voltage = 0.0;
float temp=0.0;
int analog_value;
String logger;
// A simple data logger for the Arduino analog pins

// how many milliseconds between grabbing data and logging it. 1000 ms is once a second
#define LOG_INTERVAL  1000 // mills between entries (reduce to take more/faster data)

// how many milliseconds before writing the logged data permanently to disk
// set it to the LOG_INTERVAL to write each time (safest)
// set it to 10*LOG_INTERVAL to write all data every 10 datareads, you could lose up to 
// the last 10 reads if power is lost but it uses less power and is much faster!
#define SYNC_INTERVAL 1000 // mills between calls to flush() - to write data to the card
uint32_t syncTime = 0; // time of last sync()

#define ECHO_TO_SERIAL   1 // echo data to serial port
#define WAIT_TO_START    0 // Wait for serial input in setup()


RTC_DS1307 RTC; // define the Real Time Clock object

// for the data logging shield, we use digital pin 10 for the SD cs line
const int chipSelect = 10;

// the logging file
File logfile;

void error(char *str)
{
  Serial.print("error: ");
  Serial.println(str);

  while(1);
}

void setup(void)
{

  lcd.begin(16, 2); 
   lcd.setCursor (0,0);
   lcd.print(" Arduino based ");
   lcd.setCursor(0,1); 
   lcd.print("Digital Voltmeter");
delay(2000);

  Serial.begin(9600);
  Serial.println();
  

  
#if WAIT_TO_START
  Serial.println("Type any character to start");
  while (!Serial.available());
#endif //WAIT_TO_START

  // initialize the SD card
  Serial.print("Initializing SD card...");
  // make sure that the default chip select pin is set to
  // output, even if you don't use it:
  pinMode(10, OUTPUT);
  
  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    error("Card failed, or not present");
  }
  Serial.println("card initialized.");
  
  // create a new file
  char filename[] = "LOGGER00.CSV";
  for (uint8_t i = 0; i < 100; i++) {
    filename[6] = i/10 + '0';
    filename[7] = i%10 + '0';
    if (! SD.exists(filename)) {
      // only open a new file if it doesn't exist
      logfile = SD.open(filename, FILE_WRITE); 
      break;  // leave the loop!
    }
  }
  
  if (! logfile) {
    error("couldnt create file");
  }
  
  Serial.print("Logging to: ");
  Serial.println(filename);

  // connect to RTC
  Wire.begin();  
  if (!RTC.begin()) {
    logfile.println("RTC failed");
#if ECHO_TO_SERIAL
    Serial.println("RTC failed");
#endif  //ECHO_TO_SERIAL
  }
  

  logfile.println("seconds,stamp,datetime,input voltage");    
#if ECHO_TO_SERIAL
  Serial.println("seconds,stamp,datetime,input voltage");
#endif //ECHO_TO_SERIAL
 
  // If you want to set the aref to something other than 5v
  analogReference(EXTERNAL);
}

void loop(void)
{
  DateTime now;

  // delay for the amount of time we want between readings
  delay((LOG_INTERVAL -1) - (millis() % LOG_INTERVAL));
  

  
  // log seconds since starting
  uint32_t m = millis();
  logfile.print(m / 1000);           // secons since start
  logfile.print(", ");    
#if ECHO_TO_SERIAL
  Serial.print(m / 1000);         // seconds since start
  Serial.print(", ");  
#endif

analog_value = analogRead(A0);
temp = (analog_value * 5.0) / 1024.0; 
voltage = temp/(0.0909);

  // fetch the time
  now = RTC.now();
  // log time
  logfile.print('"');
  logfile.print(now.year(), DEC);
  logfile.print("/");
  logfile.print(now.month(), DEC);
  logfile.print("/");
  logfile.print(now.day(), DEC);
  logfile.print(" ");
  logfile.print(now.hour(), DEC);
  logfile.print(":");
  logfile.print(now.minute(), DEC);
  logfile.print(":");
  logfile.print(now.second(), DEC);
  logfile.print('"');
  logfile.print("  voltage = ");
  logfile.print(voltage);
#if ECHO_TO_SERIAL
  Serial.print('"');
  Serial.print(now.year(), DEC);
  Serial.print("/");
  Serial.print(now.month(), DEC);
  Serial.print("/");
  Serial.print(now.day(), DEC);
  Serial.print(" ");
  Serial.print(now.hour(), DEC);
  Serial.print(":");
  Serial.print(now.minute(), DEC);
  Serial.print(":");
  Serial.print(now.second(), DEC);
  Serial.print('"');
  Serial.print("  voltage = ");
  Serial.print(voltage);
#endif //ECHO_TO_SERIAL


   
   
   if (voltage < 0.1) 
   {
     voltage=0.0;
   } 
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Voltage= ");
    lcd.print(voltage);
    lcd.setCursor(13,1);
    lcd.print("V");
    delay(30);



  logfile.println();
#if ECHO_TO_SERIAL
  Serial.println();
#endif // ECHO_TO_SERIAL



  // Now we write data to disk! Don't sync too often - requires 2048 bytes of I/O to SD card
  // which uses a bunch of power and takes time
  if ((millis() - syncTime) < SYNC_INTERVAL) return;
  syncTime = millis();
  
}